Thermodynamic aspects of freeze-drying: A case study of an “organic solvent–water” system

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Abstract

Aqueous solutions of glycine and tetrahydrofuran (THF) were frozen under variable conditions and subsequently annealed. The phases that resulted from this process were studied by X-ray diffraction, DSC and cryotemperature SEM. Under conditions achieved in common laboratory freeze-dryers, the THF clathrate hydrate of cubic structure II was formed in near-quantitative yields. The temperature–composition state diagram for the THF–water–β-glycine systems suggests that the critical temperature of the primary drying stage is the temperature of the four-phase peritectic reaction (269 K), and not the temperature of the congruent melting of the THF hydrate in the THF–water system (278 K). Freeze-drying is shown to go much faster if aqueous solutions are substituted for THF–water solutions. This finding is of great importance for practical applications, including pharmaceutical drug formulation.

Original languageEnglish
Pages (from-to)1593-1604
Number of pages12
JournalJournal of Thermal Analysis and Calorimetry
Volume127
Issue number2
DOIs
Publication statusPublished - 1 Feb 2017

Keywords

  • Cryotemperature SEM
  • DSC
  • Freeze-drying
  • Phase diagram
  • X-ray diffraction
  • COSOLVENT SYSTEMS
  • TERTIARY BUTYL ALCOHOL
  • THERMAL-EXPANSION
  • DRUG-DELIVERY
  • PARTICLE ENGINEERING TECHNOLOGY
  • ICE MORPHOLOGY
  • FROZEN-SOLUTIONS
  • TETRAHYDROFURAN CLATHRATE HYDRATE
  • HEAT-CAPACITIES
  • ENHANCE DISSOLUTION

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